JP2008209935A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve magnification error and improve image quality, taking into account of paper slip and so on in the setting of paper feed resist and fixing linear velocity. <P>SOLUTION: The image output apparatus includes: a resist roller 491, which aligns the leading end of paper by temporality stopping the paper in order to synchronize the leading end of the paper fed from a double-sided unit 450 and a first tray 451 and the leading end of an image formed by a photoreceptor 440; a fixing device 493 for fixing an unfixed image formed on the paper by a photoreceptor 440; an image processing controller for varying the paper conveyance speed of the fixing device 493 relative to the double-sided unit 450, the first tray 451 and the resist roller 491; a paper feed tray controller; and a system controller for controlling a fixing condition according to a paper type. The system controller exerts control so as to vary a linear velocity set value for the image processing controller and a paper feed tray controller according to at least any one of the paper type, the paper size, or the fixing condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a sheet on which an image is recorded is generally a type that feeds a cut sheet stored in a sheet feeding cassette. There is a limit to the length of paper that can be stored in the paper cassette. In view of this, a type that stores paper wound around a reel, cuts the paper into a predetermined length, and feeds the paper is used because a wide and long paper can be obtained. In these two types of image forming apparatuses as well, when forming an image, the leading edge of the paper is synchronized with the leading edge of the image created by the image forming unit formed of an image carrier such as a photoconductor. Therefore, the paper is temporarily stopped by the registration roller, the registration at the leading edge of the paper is aligned, the image is recorded on the paper by the image forming unit, the unfixed image on the paper is fixed by the next fixing unit, and then discharged. It is like that.

  In the image output device that feeds the latter long paper, transfers the image to the paper by the image forming means, and fixes the image by the fixing device, the long paper is output from the fixing device without being skewed. In order to prevent the occurrence of wrinkles and image blurring, a back tension is applied to the paper and the paper is conveyed straight. Applying back tension to such a sheet to prevent skew feeding is also carried out in an image forming apparatus that can use a cut sheet having a size larger than the former B4 or A4.

  However, in this method, since the back tension is applied to the paper at the rear end portion of the paper, the paper conveyance speed is faster than that of the image carrier, the image is stretched, and an error is caused in the magnification. It was. In order to prevent the expansion of these magnifications and the like, control means for setting the fixing linear speed slower than the process speed has also been proposed, but there is a limit to the conveyance of long paper, and the paper tends to be pulled. The conveyance is more stable when the linear speed of fixing is set faster and the linear speed setting with the back tension applied.

  The present invention has been made in view of such a demand, and its purpose is a paper feed resist for applying back tension to the paper and a fixing linear speed setting, taking into account paper slip and the like, and the paper type and paper size. The line speed is set according to the above, the magnification error is improved, and the image quality is improved.

  In order to achieve the above object, the first means temporarily stops the paper in order to synchronize the paper feeding / conveying roller that feeds the paper and the leading edge of the paper and the leading edge of the image formed by the image forming unit. A registration roller for aligning the registration at the leading edge of the paper, a fixing device for fixing the unfixed image formed on the paper by the image imaging unit, and a paper conveyance speed of the paper feeding conveyance roller, the registration roller, and the fixing device. In an image output apparatus including a conveyance driving unit capable of changing a linear speed and a control unit that controls a fixing condition according to a paper type, the control unit includes at least a paper type, a size, and a fixing condition. The linear velocity by the conveyance driving means is set by either of them.

  In this case, according to the second means, the control means increases the linear velocity so that a difference between the fixing linear velocity and the resist linear velocity or the paper feeding linear velocity is widened as the width of the paper to be passed becomes narrower. Set.

  According to the invention of the present application, since each conveyance speed can be changed for each paper type, paper size, and each fixing condition, the occurrence of skew can be prevented, the conveyance quality can be improved, and the magnification error can also be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing the configuration of a wide digital copying machine according to an embodiment of the present invention. In this wide digital copying machine, a copying machine main body 200 is mounted on a paper feeding device 100 and a reading device (scanner unit) 300 is mounted on the copying machine main body 200 to constitute a copying apparatus as a whole. Then, the originals placed on the original table 301 of the reading apparatus 300 are fed one by one to the reading apparatus 300, the image of the original is read by the contact image sensor (CIS) 302, and the original after reading is a discharge tray. It is configured to discharge the paper upward.

  The document on the document table 301 is aligned in the width direction by a side fence (not shown), fed by the feed roller 303, and conveyed below the contact image sensor 302. A document width detection sensor and a document length detection sensor (both not shown) are provided on the document table 301. These sensors detect the size of the document sent from the document table 301. Although the structure of the document under the contact image sensor 302 is not shown, it is exposed by a light source such as an LED array or a fluorescent lamp, and the reflected light is passed through the rod lens array to form an image on the contact image sensor 302, and the photoelectric Perform conversion. After the reading of the original is completed, the paper is discharged onto the paper discharge tray by the transport roller 304 and the paper discharge roller 305.

  The copying machine main body 200 includes an image forming unit 201, a fixing unit 202, and a paper discharge unit 203. An image signal read by the contact image sensor 302 is subjected to image processing, and a charger ( An electrostatic latent image is formed on the uniformly charged photoconductor 205 by (not shown). The electrostatic latent image is transferred to a recording sheet fed from the sheet feeding device 100 to copy the original image, and the sheet is provided on the upper surface of the copying machine main body 200 through the paper discharge unit 203. The paper is discharged to a paper discharge tray 206 or a paper discharge tray 207 provided behind the copier body 200.

  The paper feeder 100 has two upper and lower roll paper trays 101 and 102. These roll paper trays 101 and 102 can be pulled out in the left direction in FIG. 1 from the apparatus housing, and are configured to perform roll paper setting and jam processing with the tray pulled out. Two roll papers can be set on each of the roll paper trays 101 and 102. The roll papers 103 to 106 wound around the paper tube are set in the paper feeding device 100 via a pair of paper holders 107 to 110.

  Paper feed rollers 111 to 114 for the roll papers 103 to 106 are arranged in the vicinity of the roll papers 103 to 106. The paper sent out by the paper feed rollers 111 to 114 is cut into a predetermined length by roll cutter units 115 and 116 provided on the front side of the tray (left side in FIG. 1), and sent to the copying machine main body 200. . The cut and fed paper is synchronized with the image forming timing by the registration roller 208 and guided to the photosensitive member 205.

  The image formed on the photosensitive member 205 is transferred to the sheet by the transfer unit 209, separated from the photosensitive member 205 by the separation unit 210, and guided to the fixing unit 202 by the conveyance belt 211 to thermally fix the image. Is done. The sheet on which the image is fixed is discharged by discharge rollers 212 and 213 that form a discharge unit 203. The paper discharge direction is switched by the branching claw 214 and becomes a paper discharge tray 206 on the upper surface of the copier body 200 or a paper discharge tray 207 on the rear side of the copier body 200.

  A paper discharge sensor 215 is provided between the fixing unit 202 and the paper discharge roller 212, and a paper discharge sensor 216 is provided between the paper discharge roller 212 and the paper discharge roller 213. Whether or not the sheet is in the sheet discharge unit 203 can be determined by 216. Although not shown, the copying machine main body 200 is provided with drive control means for driving the paper discharge rollers 212 and 213, and the reading device 300 has an operation start instruction and repeat copy, which is information on paper to be conveyed. And an operation unit for inputting long sheet passing information.

  Next, the configuration of the image forming apparatus to which the present invention is applied will be described with reference to FIG. 2 using a digital copying machine that feeds cut sheets as an example. This digital copying machine generally includes a copying machine main body 400, an automatic document feeder (ADF) 401, a paper discharge tray 402, and a paper feed unit (bank) 403. The automatic document feeder 401 feeds the documents stacked on the document feeding table 404 one by one onto the contact glass 405 on the copying machine main body 400 side, and discharges them onto the discharge tray 406 after reading the image. It is configured.

  The document on the document feeder 404 is aligned in the width direction by a side fence (not shown), separated from the lowermost document by the feed roller 407, fed, and fed onto the contact glass 405 by the transport belt 408. Paper. The feeding unit 409 is provided with a document width detection sensor 410 and a document length detection sensor 411. By these sensors, the size of the document sent from the automatic document feeder 401 is detected.

  When reading a double-sided original, the original on the original feeder 404 is separated from the lowermost original by the paper supply roller 407 and fed, and passes through the contact glass 405 by the conveyor belt 408. After being reversed by the reversing claw 413, the sheet is again fed onto the contact glass 405 and the back surface is read. The original on the contact glass 405 is transported by the transport belt 408 after being read from the back surface, reversed by the reversing claw 413, fed again onto the contact glass 405, and the front surface is read. The document after the front surface reading is completed is discharged onto the discharge tray 406 by the conveyance belt 408 and the discharge roller 412.

  The copying machine main body 400 includes a scanner that reads a document, an image processing unit, a plotter, and the like. The scanner includes a contact glass 405 for placing a document and an optical scanning system. The optical scanning system includes an exposure lamp 420, a first mirror 421, a second mirror 422, a third mirror 423, a lens 424, a full color CCD 425, and the like. Have The exposure lamp 420 and the first mirror 421 are mounted on a first carriage (not shown), and the first carriage moves in the sub-scanning direction at a constant speed by a stepping motor when reading a document.

  The second mirror 422 and the third mirror 423 are mounted on a second carriage (not shown), and the second carriage is moved by a stepping motor at half the speed of the first carriage when reading a document.

  The original on the contact glass 405 is optically scanned by the movement of the first and second carriages, and is imaged on the light receiving surface of the CCD 425 by the lens 424 and subjected to photoelectric conversion.

  The image signal separated into each color of red (R), green (G) and blue (B) by the full color CCD 425 is subjected to various image processing by the image processing unit 604 after A / D conversion or the like by the image processing circuit. Then, at the time of copying, the writing unit copies the recording paper. The writing unit includes a laser output unit 430, an fθ lens 431, and a mirror 432. The laser output unit 430 includes a laser diode (LD) as a laser light source, a polygon mirror and a polygon motor (not shown).

  The laser output unit 430 emits a black signal laser beam modulated according to the image read by the scanner during copying, and forms a latent image on the photoconductor 440. Around the photosensitive member 440, a black developing unit 441, an LED writing unit 442 for writing a red signal image, a red second developing unit 443, a transfer unit and a separator (not shown), and the like are arranged. The upper toner image is recorded on the paper.

  The paper is selectively fed from one of the duplex unit 450 and the first tray 451 in the copier body 400 and the second tray 452, the third tray 453, and the fourth tray 454 in the paper feed unit 403, respectively. The paper is fed by the roller pair of the separation roller 456, the first paper feeding device 457, the second paper feeding device 458, the third paper feeding device 459, and the fourth paper feeding device 460.

  As shown in FIG. 3, the size and setting direction of the recording paper set in each tray, the position of the size lever 470 in the tray, and the combination of ON / OFF of a plurality of push switches 471 are provided for each tray described above. It is configured to detect.

  The paper fed from the duplex unit 450 and the first tray 451 is transported upward by the vertical transport unit 480, and the paper fed from the second tray 452, the third tray 453, and the fourth tray 454 is It is transported upward by the bank vertical transport unit 481 and the vertical transport unit 480.

  The sheet conveyed upward hits the registration roller 491 after a predetermined time after its leading edge is detected by the registration sensor 490 and temporarily stops.

  Then, it is conveyed by the registration roller 491 in synchronization with the sub-scanning effective period signal (FGATE), and the toner image on the photosensitive member 440 is transferred.

  Next, the sheet is separated from the photoconductor 440 and then conveyed by the conveying device 492, and the toner image is fixed by the fixing device 493. The fixed sheet is discharged to the discharge tray 402 by the switching claw 494 and the discharge roller 495 during single-sided printing and after double-sided printing is completed.

  The paper on which printing has been completed only on the front surface during duplex printing is guided to the duplex conveyance path 496 by the switching claw 494, reversed by the feed roller 455 and the separation roller 456, and accumulated on the duplex unit 450. The sheet on the duplex unit 450 comes into contact with the feed roller 455 as the tray rises, and is fed to the vertical conveyance unit 480 when the feed roller 455 rotates, and an image is formed on the back surface of the photoreceptor 440 again. .

  FIG. 4 is a block diagram showing the control system of the two digital copying machines described above. In the figure, an operation unit controller 500 performs liquid crystal display and various LED display controls and various key input controls on the operation unit, and a system controller 501 performs sheet feeding, conveyance, fixing, duplex printing, process control, and the like. The image processing controller 502 performs image control and scanner reading control, and the ADF controller 503 controls the automatic document feeder 100.

  The paper feed tray controller 504 controls the paper feed tray, the fax controller 505 performs fax transmission / reception management and file management, and the printer controller 506 performs printer data reception management and file management.

  FIG. 5 is a block diagram showing an image processing circuit of the digital copying machine described above. In the figure, a document 600 on the contact glass 10 is illuminated by the exposure lamp 11 and the reflected light is read by the color CCD 16.

  The analog image signal separated into R, G, and B by the color CCD 16 is amplified and corrected by the signal processing circuit 601, converted to a digital image signal by the AD converter 602, and further converted by the shading correction circuit 603. After the shading correction, the image is sent to the image processing unit 604.

  The image processing unit 604 performs image quality processing such as MTF correction, γ correction, black image generation, color image generation, binary processing, and multi-value processing, and outputs black data and color data to the selector 605. In the selector 605, the destination of the image signal is switched to the scaling unit 606 or the image memory controller 608. The image signal that has passed through the scaling unit 606 is enlarged / reduced in accordance with the scaling factor and sent to the writing unit 607. The image memory controller 608 and the selector 605 are configured to be able to input and output image signals in both directions.

  Also provided are a CPU 609 for setting the image memory controller 608 and the like and controlling the reading unit and writing unit, and a ROM 610 and a RAM 611 for storing the program and data. Further, the CPU 609 writes and reads data in the image memory 612 via the memory controller 608.

  The image of the original image sent to the image memory controller 608 is sent to the image memory 612 after the image data is compressed by an image compression device in the image memory controller 608. By performing image compression, a limited image memory can be used effectively. In addition, since a large amount of original image data can be stored at a time, the stored original image data can be output in page order. In this case, when the image is output, the data in the image memory 612 is output while being sequentially expanded by the expansion device in the memory controller 608.

  At the time of FAX transmission, black data is transferred to the FAX image memory 613 by the selector 605. At the time of FAX reception, the received data is demodulated and expanded from the line, and is expanded in the FAX image memory 613 and then sent to the writing unit 607 by the selector 605. Further, when the printer data is received, the data is expanded in the printer image memory 614 and then sent to the writing unit 607 by the selector 605.

  Next, the internal configuration of the fixing unit 202 in the digital copying machine of FIG. 1 and the fixing device 493 in the digital copying machine of FIG. 2 will be described with reference to FIG. The fixing device 202 or 493 includes a fixing roller 700 and a pressure roller 701 that is in pressure contact with the fixing roller 700. The surface of the fixing roller 700 is coated with a heat-resistant release layer such as PFA or PTFE, and a heat source 702 is provided inside. As the heat source 702, a halogen heater, an infrared heater (nichrome wire), or the like is used.

  A fixing temperature sensor 703 as temperature detecting means is provided on the peripheral surface of the fixing roller 700, and a pressure temperature sensor 704 as temperature detecting means is provided on the peripheral surface of the pressure roller 701. This fixing temperature sensor. 703. Based on the temperature detection signal from the pressure temperature sensor 704, the heat source 702 is controlled so that the temperature of the fixing roller 700 and the pressure roller 701 becomes a certain temperature, and the amount of heat supplied to the paper is controlled. Therefore, the pressure mechanism is controlled so that the nip width between the fixing roller 700 and the pressure roller 701 can be changed.

  The fixing roller 700 is rotated by a driving mechanism (not shown), and performs fixing processing by applying heat and pressure to the sheet while conveying the sheet in cooperation with the pressure roller 701. The pressure roller 701 has a surface made of a heat-resistant rubber layer such as silicon rubber. The pressure roller 701 is pivotally supported at both ends of the shaft so as to be rotatable, and is always urged in a direction away from the fixing roller 700 by an urging means (not shown). On the other hand, the pressure roller 701 is lifted from below the shaft by a pressure mechanism and pressed against the lower portion of the fixing roller 700.

  In the pressurizing mechanism, the stepping motor 710 rotates forward (in the direction of the arrow A), and the gear 713 is driven from the coaxial gear 711 through the idler gear 712. The shaft of the gear 713 is a feed screw 714 that pulls the anchor 715 horizontally in the direction of arrow C. One end of a spring 716 is hung on the anchor 715, and the other end of the spring 716 is hung on a link 717. As the anchor 715 moves horizontally, the link 717 rotates around the fulcrum 718. A lever 719 is fitted to one end of the link 717 and rotates around a fulcrum 720 to push up the pressure roller 701 and apply pressure.

  Further, when the stepping motor 710 rotates in the reverse direction (B direction), the anchor 715 is pushed back horizontally in the direction of arrow D, the lever 719 rotates about the fulcrum 720, and the pressure roller 701 is pulled down to release pressure. At this time, the anchor 715 is provided with a home position detection sensor 721, and the instructed pressure can be applied to the pressure roller 701 by adjusting the amount of movement of the anchor 715 by the home position detection sensor 721. . This mechanism is provided at both ends of the pressure roller 701.

  As soon as the digital copying machine is turned on, the heat source 702 is activated to start heating the fixing roller 700, and the surface temperature of the fixing roller 700 and the pressure roller 701 is determined by the fixing temperature sensor 703 and the pressure temperature sensor 704. Detection is started. When the surface temperature of the fixing roller 700 and the pressure roller 701 reaches a temperature at which an unfixed image on the sheet can be fixed, copying can be started, and this is displayed on an operation panel (not shown).

  A heat roller fixing device comprising a combination of a fixing roller incorporating a heater as described above and a pressure roller is known. The temperature control of the fixing device of this type is a so-called on-off control in which the temperature is controlled while alternately supplying and not supplying power to the heater with a reference temperature (fixing temperature) generally required for performing a fixing operation. There are a control method and a so-called proportional control method in which the pulse width or pulse density of a pulse signal for controlling energization of the heater is proportionally changed as the temperature approaches the fixing temperature.

  To compensate for the disadvantages of each of these methods, the thermal fixing device is linearly started up to the proportional start point by full energization heating of the heater, and then the transition to the fixing temperature required for the fixing operation is performed while maintaining thermal equilibrium by proportional control. A control method is also adopted to maintain the system. In any case, in the heat roller fixing device, the fixing roller is maintained at a certain set temperature when the machine is on standby, and the sheet sent by the image output start signal is added between the fixing roller pair to apply heat. The toner on the paper is fused and fixed.

  Among the wrinkles that occur during paper conveyance in such a heat roller type fixing device, there are wrinkles that occur because the paper skews (skews) during conveyance. In particular, the cause of the skew is that the paper feed from the paper feeder is transported in a non-uniform state, the positional relationship of the units involved in each transport is not accurate, and the temperature at the fixing device Due to non-uniform distribution and non-uniform pressure distribution, the paper skews, wrinkles occur during fixing, and poor adhesion between the paper and the photoconductor occurs at the transfer section, resulting in white spots in the image. To do.

In particular, in the wide-width copying machine shown in FIG. 1 that passes a long sheet of paper, this is a major technical problem. In order to solve the problem, in the present invention,
Each line speed is set in a relationship of sheet feeding line speed <registration line speed ≦ photosensitive member linear speed <fixing line speed, that is, the line speed of each transport system based on the roll sheets 103 to 106 set in the sheet feeding device 100. In order to prevent wrinkles and white spots, the paper is fed with a tension that is always applied with a tension to prevent the occurrence of skew.

  This conveyance technique can also be applied to a copying machine of a popular machine that feeds cut paper as shown in FIG. 2, and in particular, due to the recent downsizing of the machine, the space between the fixing and the photoconductor is narrowed, and white due to paper skew is reduced. The margin of omission and wrinkle is disappearing, and it can be applied as a measure to prevent skew.

  However, this conveyance method is set so that the linear velocity of the sheet coincides with the linear velocity of the sheet when the fixing linear velocity is faster than the set value of the photosensitive member linear velocity and the back tension is effective. However, if the paper in the paper feed section is cut or the rear edge of the paper passes through the transport rollers, the back tension gradually weakens, and the paper is transported at the speed of the photosensitive member by pulling the fixing paper. Since the image becomes faster, the image transferred onto the paper is stretched in the transport direction (sub-scanning direction), and a magnification error occurs.

  In order to solve this problem, the present invention controls the fixing linear velocity setting value to a setting value with a small magnification error according to the paper type and paper size, and also controls the conveyance speed during the conveyance of the paper so While applying tension, control is performed to match the speed of the paper with the speed of the photosensitive member, thereby improving the conveyance quality and the image quality.

  Hereinafter, the control procedure in the first embodiment will be described with reference to FIG. FIG. 7 is a flowchart for explaining the control procedure in the first embodiment. First, the paper size and paper type are checked (step 101). In the case of the wide-width copying machine shown in FIG. 1, a method is adopted in which the operator sets the paper size and paper type of the paper feed stage for each paper feed stage from the operation unit. In the case of the copying machine that feeds the cut sheet shown in FIG. 2, the sheet size is detected by the size lever 470 in FIG. 3 that sets the sheet size in the sheet feeding tray.

  Next, five fixing conditions such as fixing temperature and pressure can be selected according to the paper thickness for each paper type. From among these, fixing conditions are set (step 102), and the paper feed stage to be output Is designated (step 103). This confirms the paper size and paper type (plain paper, tracing paper, film) set in the paper feed stage and determines the fixing conditions. , Fixing) is determined (step 104), and paper feeding is started (step 105).

The set value of the fixing speed is set so that the linear speed increases as the paper width decreases according to the size, and film ≦ plain paper <tracing paper for the paper type. In the copying machine described with reference to FIGS. 1 and 2, the speed of the registration rollers and the paper feed speed are constant, but there are speed fluctuations due to paper slip and the like. Therefore, the conveyance quality can be improved.

  The reason for changing the linear speed according to the size of the paper to be fed is that the narrow paper size is more likely to be skewed. When the paper size is continuously passed, the temperature of the non-sheet passing part of the fixing pressure roller rises, the surface pressure of the sheet passing part that actually passes the paper decreases, the slip increases, and the paper transport speed Therefore, the smaller the paper width is, the faster it is set in advance.

  8 to 11 are graphs for explaining a method for increasing the back tension. FIG. 8 shows the relationship between the paper width and the speed ratio when the resist conveyance speed and the photosensitive member linear speed are constant and the fixing linear speed is changed. FIG. 9 is a graph showing the relationship between the paper width and the speed ratio when the photosensitive member linear velocity is constant and the resist conveyance speed and the fixing linear velocity are changed. FIG. 10 is a graph showing the relationship between the resist conveyance speed and the photosensitive member linear velocity and the fixing line. FIG. 11 is a graph showing the relationship between the paper type and the speed ratio when the speed is changed. FIG. 11 shows the relationship between the paper type and the speed ratio when the photosensitive member linear speed is constant and the resist conveyance speed and the fixing linear speed are changed. It is a graph.

  As shown in FIG. 8 and FIG. 10, the method of increasing the back tension includes the method of increasing the back tension by increasing the fixing linear speed while maintaining the resist conveyance speed and the photosensitive member linear speed as shown in FIGS. As shown, there is a method in which the photoreceptor linear velocity is constant, the fixing linear velocity is increased, and the resist linear velocity is decreased to increase the back tension. In both cases, the difference between the fixing linear velocity and the resist linear velocity is the amount of back tension, so the amount of back tension is the same. However, when the paper length is short, the former method, where only the fixing linear velocity is increased, is magnified. There is little variation in error.

  On the contrary, when the paper is long (the longer the back tension is applied), the latter has a smaller magnification error deviation. Therefore, it is also effective to switch the method of applying the linear velocity difference depending on the length of the paper. In this embodiment, the speed of the resist linear speed is changed. However, the paper feed linear speed may be changed.

  In the second embodiment of the present invention, the initial speed (Vr0) of the registration roller, the initial fixing speed (Vh0), the deceleration time (T1) of the paper, and the speed of the registration roller after T1, depending on the type of paper and the fixing conditions. (Vr1), fixing speed (Vh1), and the like are determined. Hereinafter, a description will be given with reference to FIGS. FIG. 12 is a flowchart for explaining a control procedure in the second embodiment, FIG. 13 is a diagram for explaining a sheet state between the photosensitive member and the fixing device, and FIG. 14 is a registration roller speed set according to the sheet type. FIG. 15 is a table showing registration roller speed and fixing speed set according to the paper width.

  As in steps 101 to 105 of the first embodiment described above, first, the paper size and paper type are checked (step 201), the fixing conditions are set (step 202), and the paper feed stage to be output is designated. Then (step 203), each conveyance speed is determined based on the paper size of the paper feed stage, the paper type and the fixing conditions (step 204), and paper feed is started (step 205). Also, depending on the type of paper and fixing conditions, the initial speed (Vr0) of the registration roller, the initial speed of fixing (Vh0), the deceleration time of the paper (T1), the speed of the registration roller after T1 (Vr1), and the fixing speed (Vh1). Is determined.

  At this time, if the flow of the paper is taken as an example in the case of the copying machine of FIG. 1, the registration sensor (not shown in FIG. 1, but installed in the vicinity of the registration roller pair 208) is turned on at the leading edge of the paper. Then, the front end is added to the registration roller 208 (some machines may be held in contact with the nip of the registration roller) and wait until an image write signal (Fgate) signal is output. When the image writing signal is received, the paper starts and the paper is conveyed as shown by the solid line in FIG. The sheet starts the registration roller 208 and the time is counted (step 207).

  Each linear velocity has a relationship of Vr0 = Vd <Vh0 when the velocity of the registration roller pair 208 is Vr0 and the photosensitive member linear velocity is Vd, and the velocity of the registration roller pair 208 is Vr0 and the fixing linear velocity. Is set to Vh0 (step 208). As a result, the sheet is pulled by the fixing unit 202 and enters the broken line state shown in FIG. At this time, the back tension works on the paper, and skew is prevented.

The time (T1) at this time is
T1 = T01 + (L0−L1) / (Vh0−Vr0)
Calculated by Here, T01 is the time until the leading edge of the sheet starts the registration roller 208 and enters the nip of the fixing unit 202, and L0 is the transport distance by which the leading edge of the sheet is transported from the transfer position of the photosensitive member to the fixing nip. In FIG. 13, a solid line portion L1 indicates a linear distance (broken line portion in FIG. 13) between the transfer portion 209 of the photosensitive member 205 and the nip of the fixing portion 202. In this embodiment, since each speed changes depending on the paper type, paper size, and fixing conditions (the operator can change the setting depending on the paper thickness), T1 is calculated by the above formula.

  Next, it is checked whether or not the time count value t has passed T1 (step 209). If T1 has passed, the resist speed is changed to Vr1, and the fixing speed is changed to Vh1 (step 210).

The relationship of the linear velocity at this time is Vr1 <Vd ≦ Vh1
It has become. Accordingly, the conveyance speed at the transfer unit is set to be the linear velocity Vd of the photosensitive member while maintaining the back tension of the sheet.

  Vh1 matches the linear velocity of the photosensitive member 205 when the paper back tension is applied. Therefore, when the roll paper is cut and the back tension is reduced, the transfer of the paper at the transfer portion of the paper is performed. The speed is faster than the speed of the photoreceptor. This is the same when the trailing edge of the paper passes through the registration roller, and the back tension is eliminated, so that the speed at the paper transfer portion is increased.

  Therefore, in the case of roll paper feeding, if the time when the trailing edge of the sheet is cut is T2, and the time when the trailing edge is removed from the registration roller is T3, it is determined whether or not the time count t has reached T2. A check is made (step 211), and if reached, the fixing speed is changed to Vh2 (step 212). Next, it is checked whether or not the time count t has reached T3 (step 213), and if it has reached, the fixing speed is changed to Vh3 (step 214).

Here, the relationship between the linear velocities is Vr1 <Vd = Vh3 ≦ Vh2 ≦ Vh1
There is a relationship.

  In this embodiment, the time count is performed from the registration start, but this count start position is counted from the paper feed start or the paper discharge sensor on after fixing, and the time spent for the transport is considered accordingly. Of course, it is also possible.

  On the other hand, the slip rate of each transport means differs depending on the paper type of the paper, and the margin for occurrence of skew also differs depending on the paper type. In general, tracing paper or the like is likely to be curled at the front end of the paper due to environmental humidity, and therefore the paper itself is easily skewed. Accordingly, the conveyance is not stable unless the amount of back tension of the paper is not more than that of plain paper. Therefore, Vr0, Vr1, Vh0, Vh1, Vh2, and Vh3 are set to different values depending on the type of paper.

The value is controlled to be set as shown in FIG. Here, α is a paper type coefficient, and the set value is set for each paper type by the paper type coefficient α. Of course, this is done for each paper type in the operation unit.
1 ≦ α ≦ 1.0005
Since the change can be made according to the paper type used in the operation, the transport quality can be further improved.

Here, when the paper type coefficient α is αp for plain paper, αt for tracing paper, and αf for film, the initial setting is
1 ≦ αf ≦ αp ≦ αt ≦ 1.005
Is set to a relationship.

  This paper type coefficient changes T1 or changes the above speed. Furthermore, as shown in FIG. 15, the transport quality can be further improved by changing the speed according to the paper size (paper width).

1 is a diagram illustrating a configuration of a wide digital copying machine according to an embodiment of the present invention. FIG. It is a figure explaining the structure of the digital copying machine which feeds the cut paper based on another embodiment of this invention. FIG. 3 is a partially enlarged perspective view showing the configuration of each tray in FIG. 2. FIG. 3 is a block diagram showing a control system of the digital copying machine of FIGS. 1 and 2. FIG. 3 is a block diagram showing an image processing circuit of the digital copying machine of FIGS. 1 and 2. FIG. 3 is a partial perspective view for explaining an internal configuration of a fixing device in the digital copying machine of FIGS. 1 and 2. It is a flowchart explaining the control procedure in the 1st Embodiment of this invention. 7 is a graph showing the relationship between the paper width and the speed ratio when the resist conveyance speed and the photosensitive member linear velocity are constant and the fixing linear velocity is changed. 6 is a graph showing the relationship between the paper width and the speed ratio when the photosensitive member linear velocity is constant and the resist conveyance speed and the fixing linear velocity are changed. 6 is a graph showing the relationship between the paper type and the speed ratio when the resist conveyance speed and the photosensitive member linear velocity are constant and the fixing linear velocity is changed. 5 is a graph showing the relationship between the sheet type and the speed ratio when the photosensitive member linear velocity is constant and the resist conveyance speed and the fixing linear velocity are changed. It is a flowchart explaining the control procedure in the 2nd Embodiment of this invention. FIG. 10 is a diagram for describing a state of a sheet between a photoconductor and a fixing device according to a second embodiment. 6 is a table showing registration roller speed and fixing speed set according to the type of paper. 6 is a table showing registration roller speeds and fixing speeds set according to the paper width of paper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Paper feeding apparatus 101,102: Roll paper tray 200,400: Copier main body 201: Image forming part 202: Fixing part 205,440: Photoconductor 208,491: Registration roller 300: Reading apparatus 401: Automatic document feeder 403: Paper feed unit 425: CCD
430: Laser output unit 451-454: Tray 490: Registration sensor 493: Fixing device 500: Operation unit controller 501: System controller 604: Image processing unit 609: CPU
700: fixing roller 701: pressure roller 702: heat source 703: fixing temperature sensor 704: pressure temperature sensor

Claims (2)

A paper feeding and conveying roller for feeding the paper, a registration roller for temporarily stopping the paper to synchronize the leading edge of the paper and the leading edge of the image formed by the image forming unit, and aligning the registration at the leading edge of the paper, and the paper A fixing device for fixing an unfixed image formed by the image forming unit, a feed driving roller, a registration roller, a transport driving means capable of changing a linear speed of a paper transport speed of the fixing device, In an image output apparatus comprising a control means for controlling fixing conditions according to the paper type,
The image forming apparatus according to claim 1, wherein the control unit sets a linear velocity by the conveyance driving unit based on at least one of a sheet type, a size, and a fixing condition.   2. The control unit according to claim 1, wherein the control unit sets the linear velocity such that a difference between a fixing linear velocity and a resist linear velocity or a paper feeding linear velocity is widened as the width of the sheet to be fed is narrowed. Image forming apparatus.

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